The main goal of this project is to assess the efficacy of diindolylmethane (DIM), a bioactive compound from cruciferous vegetables, to block the malignant progression of bronchial preneoplastic lesions to lung squamous cell carcinoma (SCC) by targeting the Akt signaling pathway. Preliminary studies showed that exposure of human bronchial cells to physiologically relevant concentrations of DIM caused antiproliferative and apoptotic effects in tobacco carcinogen-transformed bronchial cells but not in normal bronchial cells. Further, we observed that DIM inhibits activation/expression of proteins involved in the Akt signaling pathway. Over- expression of constitutively activated Akt in cigarette smoke-transformed bronchial cells markedly reduced the apoptotic effects of DIM, indicating that the growth inhibitory and apoptotic activities of DIM are mediated by targeting Akt. In the present application, we will extend our studies to a mouse model of lung SCC and assess if DIM causes regression of bronchial preneoplastic lesions by inhibiting Akt activation. Moreover, we will conduct, using a molecular imaging approach, proof-of-concept studies to confirm that DIM targets Akt activation. Hypothesis: Akt activation plays a critical role in the progression of bronchial preneoplastic lesions to lung squamous cell carcinoma (SCC) and targeting Akt by DIM reverses this process. N-nitroso-tris- chloroethylurea (NTCU)-induced mouse model of lung SCC will be used to test the hypothesis. Specific Aim 1: To determine if DIM-inhibits NTCU-induced lung SCC and whether the Akt signaling pathway is the critical target for the chemopreventive activities of DIM. Specific Aim 2: To examine, using luciferase complementation-based molecular imaging platform, the role of phospho-Akt targeting on DIM-induced antiproliferative and apoptotic effects in vitro and tumor growth in xenograft models of lung cancer. Impact/Significance: The results of this study could provide a mechanistic basis and rationale for clinical trials of DIM asa chemopreventive agent in populations that are at high risk to develop lung cancer.